I agree that it would not be fair, especially to those currently receiving, or who are about to receive in the next decade or so. But, a line will eventually have to be drawn: the government will have to say, "if you're currently below age x, you'll need to start saving for your retirement with little help from the government."
Otherwise, the only way to keep benefits for everyone has been previously summarized nicely on this thread. A combination of increased taxes, decreased benefits, or a gradual raise in the retirement age.
I think this is the only way to fix the problem, permanently. The problem is that those younger taxpayers will have to make some contribution, with no hope of getting any benefits. Perhaps one way would be to divert the employee payroll tax into a 401(k), and continue the employer payroll tax for Social Security.
But, that's just a "broad stroke" proposal. There are other components of Social Security that must be addressed: survivor and disability benefits.